Electronic thermometers are widely used in the healthcare field for measuring a patient's body temperature. Typical electronic thermometers have a probe comprising an elongate shaft. Electronic temperature sensors such as thermistors or other temperature sensitive elements are contained in the shaft. In one version, the probe includes a cup-shaped aluminum tip at its free end. A thermistor is placed in thermal communication with the aluminum tip inside the probe. When a free end of the probe is placed, for example, in a patient's mouth, the tip is heated up by the patient's body and the thermistor measures the temperature of the tip. Additional electronics connected to the electronic sensor components may be contained in a base unit connected by wire to the shaft or may be contained n a handle of the shaft, for example. Electronic components receive input from the sensor components to compute the patient's temperature. The temperature is then typically displayed on a visual output device such as a seven segment numerical display device.
Disposable, removable covers for the shaft of the probe are used for hygienic purposes so the probe does not have to be cleaned and disinfected after each use. Instead, after each use of the electronic thermometer the probe cover is removed from the probe shaft and discarded, and before a subsequent use, a new clean probe cover is received on the probe. Conventionally, probe covers are made of plastic, such as a high density polyethylene (HDPE). However, the thermal conductivity of plastic is very low (0.1-0.5 W/m° C.), which can cause inefficiency in the speed and inaccuracy of the measurements taken by the thermometer. To compensate for the low conductivity of plastic, probe covers may be filled with higher conductivity materials such as aluminum and silicon oxides (1-6 W/m° C.). More recently boron nitride has been used due to its even higher conductivity (10-50 W/m° C.). Alternatively, the plastic can also be loaded with carbon black and graphite fibers (25-470 W/m° C.). However, the loading required to provide the necessary conductivity is typically high. This results in heavy parts and degraded structural properties of the plastic.